The invention relates to an apparatus for rolling up web-like or strip-like material such as paper, foil, film, textiles and the like, and more particularly but not exclusively to such an apparatus comprising rotatably mounted and motor driven winding spindles, which are individually able to be moved and located along a guide track, one respective full winding spindle being moved out of the winding position thereof after the winding operation and an empty winding spindle then being moved into this winding position substantially simultaneously. For changing the winding spindles in the winding position with a continuous supply of the material a first applying roll is brought into engagement on the wound material on the winding spindle located in the winding position and a second applying roll is moved into engagement with the wound material on the winding spindle moving out of the winding position, the applying rolls being mounted on essentially vertical pivot arms.
Such an apparatus is described in the article in the periodical "Papier+Kunststoff-Verarbeiter" No. Feb. 1985, entitled "Non-stop Wickler mit Zentralantrieb", in which case the first applying roll is suspended on pivot arms with the provision of a stationary pivot bearing. The second applying roll is mounted atop pivot arms with a provision for vertically moving the pivot bearing.
The engagement forces of the applying rolls on the wound material are of decisive importance for the quality of winding and for minimizing waste. The loading pressing or force of the applying roll on the wound material primarily influences the density of winding, that is to say the hardness of a winding. It is more particularly in the case of very thin films that the surface is not completely flat and there are differences in thickness. During winding such differences in thickness have a cumulative effect so that bulges are created. In such a case the applying roll will only be in engagement with the crests of the bulges or thicker parts so that high pressing forces would here cause very high contact forces which may well lead to the entire winding having to be rejected. Although the applying roll with a length of several meters may be up to 300 kg in weight, the pressing force on the wound material should only amount to around 10N. This means that the applying rolls should be in engagement with the respective windings in such a way that their mass is neutralized and during the winding operation as well and the changing of the finished roll engagement should be maintained with a neutralization of mass effects. Even a small pivoting of the pivot arms of the applying rolls of a few degrees will lead to very large pressing forces owing to the relevant masses.
In the case of the circular winder illustrated in FIG. 5 of the above mentioned article such a mass compensated manipulation of the applying rolls is not possible. During the winding operation the first, upper applying roll is deflected more and more owing to the increase in size of the winding or coil, since the pivot bearing is stationary. The ever increasing deflection gives rise to higher and higher engagement forces on the coil. Furthermore the lower, second applying roll is urged more and more powerfully downwards during the clearance of the completed coil so that its pressing force will become larger and larger. In the case of known circular winders suitable weight reducing means for compensation are therefore necessary for such applying forces, which are very complex and involved, since the diameter and the engagement angle are constantly changing.